Diuretics are the 1st choice for therapy of elderly hypertensives without ECG changes. Recently a lower starting dose for HCTZ in the elderly has been recommended due to observations of increased efficiency per dose, but no correlations with plasma or urine levels have been done. This study will test the hypothesis that metabolic clearance of HCTZ is diminished in the elderly compared with younger people, causing greater incidence of postural hypotension & metabolic side effects.